The cognitive neuroscience of remembering

Retrieving a memory seems to involve a set of distinct processes, with different neural substrates, that are coordinated to orchestrate the act of remembering. Recent advances in cognitive science, including brain-imaging techniques, have provided evidence for the nature of these processes. Frontal cortical areas are central to the retrieval attempt. Anterior frontal-polar cortex is activated specifically during retrieval attempts for both verbal and non-verbal material, whereas more posterior frontal cortex is activated during both retrieval and processing of verbal material. Posterior frontal activation becomes stronger as remembering becomes more difficult. Overall, frontal cortex seems to be important for strategic aspects of retrieval. A network of left-sided cortical areas, including left parietal cortex, shows activity that correlates with retrieval success. This may act as a signal to inform a person that information is from the past rather than the present. The content of a memory is probably encoded as a 'reactivation' of those areas of cortex that are activated by sensory perception in the same modality, although the systems used for perception and retrieval do not completely overlap. It is unclear to what extent early sensory cortices are activated by retrieval. Retrieval may be initiated when top–down modulation from frontal cortex interacts with sensory representation of cues to trigger reactivation of the cortical networks that represent a memory, with a network including left parietal cortex possibly signalling that the representation is old. A sense of familiarity may occur when frontal and parietal regions are activated without detailed reactivation of sensory areas, whereas detailed recollection may rely on more extensive activity to represent the content of the memory.